The present invention relates to mobile communication systems, more particularly o a technique for limiting the usage of mobile terminals existing in a specific area.
In recent years, the usage of such mobile communication systems as portable telephones and PHS terminals is rapidly spreading due to the progress in communication technologies. On the other hand, problems are arising from such a rapidly increased usage of mobile communication systems. For example, since portable telephones are usable anywhere if they are connected to the base station, they are used in such restricted places as movie theaters, playhouses, concert halls and trains where the usage of those portable telephones should be eliminated.
To cope with the above problems, there has been a conventional counter measure by announcing to the users to restrain their portable telephone uses in the restricted places. In fact, there has been no other ways but to entrust the matter to the ethics of the users. Unfortunately, it is true that the users often give in to the convenience of their portable telephones and use them carelessly in those restricted places. Even when they are consciously restraining themselves to receive calls, they might possibly forget to turn off the power or to disable vibration/ring features.
In order to limit the usage of mobile communication systems in a certain restricted area, some techniques are disclosed in Japanese Patent Prepublication No.10-145864, No.10-276473, No.10-304430, No.10-327474, No.10-328882, and No.11-8885.
For example, in one technique to limit both originating and terminating mobile terminal signals by connecting an auxiliary system to a base station, the base station needs to be modified so as to connect to the auxiliary system. In addition, if such an auxiliary system is installed in a movie theater, a leased line must be connected to the base station from the movie theater. And accordingly, this technique has to confront an impossible problem to lay such a leased line in each of moving trains, etc.